A mouthpiece for a single-reed wind instrument traditionally includes a central conduit, a cylindrical portion or bore which communicates directly with the conduit of the instrument; the other portion, or chamber, is open to the outside on the lower face of the mouthpiece. The reed is a tongue of wood disposed on the opening of this chamber, and held on the mouthpiece by a ligature.
Ligatures used for wind instruments with reeds, such as clarinets or alto and tenor saxophones, are often cloth or metal ties which hold the barrel of the mouthpiece and the reed against one another, via at least one strap retainer. The type of ligature used most often includes a metal collar, the facing ends of which are moved toward one another by way of screws known as thumb screws, which cooperate with threaded sleeves provided on these ends. Retention is thus obtained perpendicular to the axis of the barrel; the intensity of this retention must be adjusted by moving the sleeves closer to or farther away from one another.
However, such ligatures allow no more than a narrow latitude of adjustment, and it is difficult to use the same ligature for two barrels of different types of wind instrument. Two facing sleeves of the same strap retainer are in fact generally quite close to one another in their position of repose, and to adapt the ligature to a barrel one can only either tighten the thumb screws until the sleeves touch, which admits only a narrow margin of adjustment, or loosen them to space the ends of the strap retainer apart, but then one is very quickly limited by the fact that the screw threading can at most only rest on the outer surface of the barrel; if it is loosened any more, it cuts into the barrel. Because of this narrow latitude of adjustment, one type of ligature is adaptable only to certain well defined types of mouthpiece, and there are about 15 different sizes of ligatures in existence.
Wind instrument mouthpieces are also generally associated with a mouthpiece cover, which is a cap in which the instrument mouthpiece can be locked, in particular by clamping the inner edges of the cap onto the ligature. This mouthpiece cover is a protection device, which is used when one wishes to store the instrument without removing the ligature and the reed. However, the mouthpiece covers in use thus far have been relatively rigid and non-deformable elements, and the same type of mouthpiece cover cannot be used for different shapes and sizes of barrels. Furthermore, the interior of a mouthpiece cover is generally in contact with only the portion of the ligature onto which it is wedged by friction. Hence the reed of the instrument is not retained in any way except by the ligature, and it often happens that, like any moistened wood, it deforms when it dries (it is said to "leave the table"), which is detrimental to the sonority of the reed.